This project was established to apply the knowledge and techniques acquired while assessing virulence-associated components in B. pertussis to B. bronchiseptica. Isogenic sets of colonial phenotype variants are selected, cloned, and compared on three media for phenotype stability. Particular attention is paid to flagella expression, assessed by light, and scanning electron microscopy, and to 125I-surface labeling and lipopolysaccharide profiles on SDS-PAGE. Antisera are raised in mice to determine "phenotype specific" components by double diffusion, radio immune precipitate, and transfer-blotting techniques. Growth of different phenotypes in cell culture correlates pathogenicity with cytotoxicity. Both the in vitro cell culture system and in vivo infection of rats are used to assess the relative virulence of different strains and their phenotypes. By conducting studies with isogenic sets of phenotypes from different strains, the mechanisms and attributes of B. bronchiseptica infections can be studied in a more genetically controlled manner.